He arrived in the southern town to calm Bosnian Croats worried about possible repercussions of the Hague war crimes tribunal's conviction of their former military and political leaders.
"First and foremost, Croatia stands by BiH, it stands by Croats in BiH. We will do everything for Croats here to be an equal people in the long term and for this equality between the three peoples here to be respected," Plenkovic told reporters.
He and the Bosnian Presidency's Croat member, Dragan Covic, laid a wreath and lit candles at a monument to Croatian defenders at which thousands of candles have been lit recently for the six convicted Bosnian Croats, including Slobodan Praljak, who committed suicide in a courtroom of the UN court after his guilty verdict was upheld last Wednesday.
Plenkovic said that this year Croatia tried to support Croats in BiH domestically and internationally by strengthening the cooperation between the two states and the status of Croats in BiH as a constituent people.
He said next year's elections in BiH were especially important in the context of the need to change the election law.
Plenkovic also briefly talked with representatives of war victims' associations and war veterans.
Covic thanked Plenkovic for arriving in Mostar, saying that during his two-day stay they would talk about the Hague tribunal's verdict "and many other issues concerning the position of the Croat people in BiH."
Tonight they were due to hold a working dinner, while tomorrow they will meet with the leaders of the Croatian National Assembly, which brings together Bosnian Croat political parties.
Plenkovic was accompanied by Deputy Parliament Speaker Milijan Brkic and Justice Minister Drazen Bosnjakovic, among others.
Last Wednesday, the Appeals Chamber of the International Criminal Tribunal for the former Yugoslavia upheld trial chamber sentences against six former Bosnian Croat officials as participants in a joint criminal enterprise aimed at the ethnic cleansing of Muslims in which the then Croatian leadership, with President Franjo Tudjman at the helm, took part.